try the Weymouth ( and Soton?) fast ferry into St Malo too. BUT watch the booking. We once had a three hour stopover in Guernsey which although pleasant was a pain! The return ferry was good and fast but landed around Midnight in Soton IIRC. which was a bit late for the 4 hr drive back to shropshire.
We once opted to get breakfast in a nice little cafe in france rather than on the ferry. Two hours later we were waiting outside E LeClerc waiting for them to open as we had failed to find a cafe and were bloomin starving!